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Background: Proliferating pilar tumors (PPTs) are rare cutaneous neoplasms arising from hair follicles that have both malignant and metastatic potential., Objective: To present a systematic review of the epidemiology, clinical characteristics, and treatment and outcome data on PPTs., Methods: Using the OVID platform, MEDLINE and Embase were searched from inception until May 26, 2022. All studies that provided original data on PPTs in English were included. References of these studies were also cross-checked to identify any additional relevant articles. Oxford's Levels of Evidence-Based Medicine was used for quality assessment., Results: A total of 114 articles, providing data on 361 cases of PPTs, were included in our synthesis. Every study included was either a case series or case report. The mean age at diagnosis was 61.7. Most patients in the synthesis were female (71%), and the majority of cases occurred on the scalp (73.1%). The presence or absence of cytological atypia was only reported in one-third of the cases; 36.8% of cases were classified as malignant and 7.5% metastasized. Although no lesions treated with Mohs micrographic surgery required adjuvant radiation and only one reported recurrence occurred after Mohs surgery, there is insufficient data to make conclusions on a superior treatment modality., Limitations: All studies in this review were either case reports or case series., Conclusions and Relevance: Our study supports the notion that PPTs occur most commonly on the scalp of elderly female patients. Moreover, our findings confirm that PPT is capable of demonstrating aggressive biology and metastasis. Given the lack of uniformity in histologic description, pathologists should be encouraged to comment on the presence and degree of cytological atypia when reporting cases of rare neoplasms such as the PPT. Greater consensus on diagnosis and classification as well as more robust data is needed regarding optimal management., Competing Interests: Conflicts of interest None disclosed., (Copyright © 2023 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.)

Alopecia areata (AA) is a common form of nonscarring hair loss. It is believed to be a consequence of an immune-mediated stimulus, probably involving autoreactive T cells against antigens present in the hair follicle. The exact antigen is still unknown; however, some authors have proposed that melanogenesis-associated molecules might trigger autoimmunity. Although transient white hair regrowth is a common and well-known situation in AA, there are other types of white hair phenomena in this context, including permanent white hair regrowth, sparing of white hair in a patchy pattern, or sparing in a diffuse pattern, giving the appearance of the so-called overnight graying phenomena or canitis subita. In this review, we aim to describe the different clinical aspects of white hair in AA, as well as the proposed pathophysiologic mechanisms involved in this phenomena., (Copyright © 2023. Published by Elsevier Inc.)

Dermoscopy is a noninvasive diagnostic tool that is currently being used for neoplastic skin lesions, several inflammatory and infectious diseases, and skin appendage disorders. As the clinical applications of dermoscopy beyond pigmented lesions are constantly increasing, the aim of this article is to provide an update on this topic. This comprehensive review substantiates how several diseases may show peculiar dermoscopy features so as to enhance the diagnosis and avoid (in selected cases) unnecessary histologic confirmation. In other cases, dermoscopy features may be shared with other conditions, with the advantage of narrowing down the differential diagnosis by ruling out those dermatoses with similar clinical aspect but different dermoscopic presentation., (Copyright © 2018 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.)

Misdiagnosis may result from biopsy site selection, technique, or choice of transport media. Important potential sources of error include false-negative direct immunofluorescence results based on poor site selection, uninformative biopsy specimens based on both site selection and technique, and spurious interpretations of pigmented lesions and nonmelanoma skin cancer based on biopsy technique. Part I of this 2-part continuing medical education article addresses common pitfalls involving site selection and biopsy technique in the diagnosis of bullous diseases, vasculitis, panniculitis, connective tissue diseases, drug eruptions, graft-versus-host disease, staphylococcal scalded skin syndrome, hair disorders, and neoplastic disorders. Understanding these potential pitfalls can result in improved diagnostic yield and patient outcomes., (Copyright © 2015 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.)

Dermoscopic examination of hair and scalp, also named "trichoscopy," is an essential tool in diagnosis of hair and scalp diseases. Trichoscopy is fast and noninvasive and can be used to evaluate hair disorders in all body areas. Body hair disorders are uncommon, and most publications on their dermoscopic features are limited to case reports or series. In this review we present the available information on the dermoscopic diagnosis of body hair disorders including keratosis pilaris, trichostasis spinulosa, pili multigemini, circle hairs, rolled hairs, eruptive vellus hair cyst, and ingrown hairs., (Copyright © 2015 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.)

Background: Pilomatrix carcinoma is a rare cutaneous tumor derived from follicular matrix cells with few cases documented in the literature., Objective: We sought to better characterize this tumor by analyzing its epidemiologic, clinical, and histopathologic features in 13 new cases and by reviewing the literature., Methods: All cases of pilomatrix carcinoma from a large regional dermatopathology practice were identified and analyzed by chart review for clinical and histopathologic characteristics. Similar characteristics were compiled from an additional 123 cases in the English-language literature. Cox proportional hazards regression models were used to determine risk factors associated with the development of metastasis for all identified metastatic tumors., Results: Our 13 tumors were most common in middle-aged to older white men and presented mostly on the head/neck. Histopathologically, tumors were asymmetric, were poorly circumscribed, were composed of basaloid and "ghost" cells, had frequent atypical mitoses, and had infrequent lymphovascular invasion. Wide excision was considered the most definitive treatment modality, but local recurrence was common. When analyzing all reported cases of metastasis using statistics, metastasis was significantly associated (hazard ratio 3.45, P < .0413) with local tumor recurrence., Limitations: The retrospective, single-center design and the reliance on electronic medical records are limitations., Conclusions: This study helps better characterize pilomatrix carcinoma and identifies potential predictors of metastasis., (Copyright © 2014 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.)

Although traditionally known as "white forelock," poliosis circumscripta, defined as a localized patch of white hair in a group of hair follicles, can involve any hairy area on the body including the scalp, eyebrows, and eyelashes. Microscopically, poliosis demonstrates either decreased or absent melanin and/or melanocytes in the hair bulbs of the affected hair follicles. Classically, poliosis is known to occur in the setting of several genetic syndromes including piebaldism, Waardenburg, and tuberous sclerosis. In addition, poliosis has been described in association with various acquired conditions. These include inflammatory conditions, benign and malignant neoplastic entities that are mainly melanocytic, medications, and others. In this review, we aim to describe the different conditions where poliosis may be encountered, with the aim of helping the clinician to better evaluate any patient presenting with poliosis., (Copyright © 2013 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.)

Until a few years ago the diagnosis of hair shaft disorders was based on light microscopy or scanning electron microscopy on plucked or cut samples of hair. Dermatoscopy is a new fast, noninvasive, and cost-efficient technique for easy in-office diagnosis of all hair shaft abnormalities including conditions such as pili trianguli and canaliculi that are not recognizable by examining hair shafts under the light microscope. It can also be used to identify disease limited to the eyebrows or eyelashes. Dermatoscopy allows for fast examination of the entire scalp and is very helpful to identify the affected hair shafts when the disease is focal., (Copyright © 2012 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.)

Background: There are numerous reports of the value of videodermatoscopy in the clinical evaluation of alopecia. Studies performed with a handheld dermatoscope are scarce and limited to a few disease entities., Objective: The aim of this study was to evaluate the potential benefit of a handheld dermatoscope in the clinical diagnosis of alopecia., Methods: In all, 144 patients with alopecia and 144 age- and sex-matched control subjects were enrolled in the study. Diagnoses were established clinically, and confirmed by scalp biopsy in doubtful cases. Dermatoscopic examination was performed by a polarized-light handheld dermatoscope with a 10-fold magnification. The images were obtained by a digital camera with a 3-fold optical zoom., Results: The dermatoscopic patterns of circular hairs, dirty dots, epidermal scale, and pustules showed no statistically significant difference between patients and control subjects. The following features were significantly more common, or observed solely, in particular types of alopecia: hair diameter diversity, peripilar sign, and empty follicles in androgenetic alopecia; yellow dots, black dots, tapering hairs, and broken hairs in alopecia areata; absence of follicular openings, tufted hairs, white dots, follicular hyperkeratosis, pili torti, red dots, honeycomb pigment pattern, pink-white appearance, crusts, and pustules in primary cicatricial alopecias., Limitations: Evaluation of all primary cicatricial alopecias in the same cluster., Conclusions: We suggest that a polarized-light handheld dermatoscope attached to a digital camera provides a practical and useful aid for the clinical diagnosis of alopecias., (Copyright © 2011 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.)

Uncombable hair syndrome is a relatively rare anomaly of the hair shaft, with less than 100 cases reported to date, that results in a disorganized, unruly hair pattern that is impossible to comb flat. The characteristic longitudinal grooves along the hair shaft, along with the triangular or kidney-shaped cross section allows this condition to be diagnosed microscopically. The majority of cases are inherited in an autosomal-dominant manner with either complete or incomplete penetrance. There is no definitive treatment, and most cases improve with the onset of puberty.

Piloleiomyomas are benign smooth muscle tumors arising from the arrectores pilorum muscles in the skin. They usually occur as multiple firm dermal nodules located on the extremities and trunk. Solitary lesions are rare. Leiomyomas usually develop during adolescence or early adult life. Congenital pilar leiomiyoma is an extremely rare entity. We present a case of congenital solitary pilar leiomyoma located on the face.

Background: The standard methods used to diagnose scalp and hair disorders (eg, simple clinical inspection, pull test, biopsy) vary in sensitivity, reproducibility, and invasiveness. Studies on a few entities suggest that use of dermoscopy can improve clinical accuracy, but further investigation is needed., Objectives: We sought to: (1) characterize features of several nontumoral scalp and hair conditions using videodermoscopy; and (2) assess the potential usefulness of videodermoscopy in the clinical evaluation of these conditions., Methods: Images (x20-70 magnification) obtained with videodermoscopy from 220 patients with various scalp and hair disorders and 15 unaffected control subjects were reviewed for distinguishing features., Results: Conditions evaluated included psoriasis (23), seborrheic dermatitis (26), alopecia areata (58), androgenetic alopecia (64), chronic telogen effluvium (7), trichotillomania (12), and primary cicatricial alopecia (30). Clinical features evident to the naked eye were seen in great detail when videodermoscopy was used. Novel features (eg, yellow dots in alopecia areata) were also identified., Limitations: Findings require confirmation by blinded, prospective investigation., Conclusions: Use of videodermoscopy in the clinical evaluation of scalp and hair disorders improves diagnostic capability beyond simple clinical inspection and reveals novel features of disease, which may extend clinical and pathogenetic understanding.

We describe a family with woolly hair and ulerythema ophryogenes spanning four generations. Both woolly hair and ulerythema ophryogenes have been associated with Noonan syndrome and cardiofaciocutaneous syndrome (CFC), two disorders with considerable phenotypic overlap. This family did not exhibit any of the other findings characteristic of either Noonan syndrome or CFC, similar to a previously described pedigree with hereditary woolly hair. Woolly hair elicits a broad differential diagnosis, including woolly hair nevus and several genodermatoses. Our report reviews the evaluation of woolly hair and discusses the conditions associated with this physical finding.

Background: Tiger tail banding under polarizing light microscopy and hair shaft abnormalities are associated with trichothiodystrophy (TTD), a rare disorder with a wide spectrum of clinical presentations., Objective: To characterize the frequency, specificity, and extent of tiger tail banding and hair shaft abnormalities in the spectrum of TTD patients., Methods: We developed a standardized procedure for microscopic hair examination and studied hairs from 14 TTD and 4 xeroderma pigmentosum (XP)-TTD patients for tiger tail banding and hair shaft abnormalities. For comparison we examined hairs from 173 control donors consisting of 15 normals, 13 XP patients, 11 family members of XP or TTD patients, 101 patients with various cornification disorders, and 33 leukodystrophy patients. Amino acid analysis performed on hair from the TTD and XP-TTD patients showed low sulfur content., Results: Using a rotating microscope stage, all hairs in each TTD sample showed tiger tail banding under polarized light in association with a variety of hair shaft abnormalities (trichoschisis, trichorrhexis nodosa-like defects, surface irregularities, and ribboning). None of the control hairs showed tiger tail banding, and 5 of 173 controls had weathering hair shaft abnormalities., Conclusions: In patients with clinical features suggestive of TTD, tiger tail banding seen in all hairs with polarizing microscopy, in conjunction with certain hair shaft abnormalities, provides a reliable diagnostic test.

Perforating pilomatricoma is a rare clinical variant of pilomatricoma. We report a case of pilomatricoma with ulceration indicating total elimination. The lesion consisted mainly of laminating shadow cells surrounded by invaginating epidermis. We believe that this case can be considered within the category of perforating pilomatricoma.

Follicular hybrid cysts are cutaneous tumors that arise from different portions of the hair follicle. We describe a follicular hybrid cyst of the tarsus that contained features of pilomatricoma and steatocystoma and perforated the palpebral conjunctiva. The unusual location and histopathologic features are discussed.

Keratosis pilaris is found commonly in isolation as well as associated with other conditions. We describe a family with keratosis pilaris and hereditary koilonychia, with an autosomal dominant pattern of inheritance. These two findings have only been previously found in the context of monilethrix. The coexistence of the two disorders suggests a close association of their genetic pathogenesis.

Immunosuppressive drugs have been used for many years in the prevention of graft failure in transplant recipients. Although they improve morbidity and mortality after transplantation, these medications carry a significant risk of adverse mucocutaneous and systemic effects. We describe a patient receiving 4 immunosuppressive drugs who experienced persistent facial dysmorphism along with striking follicular disturbances. On histopathologic examination, the follicular structures were dilated and hyperplastic with a peculiar dysplasia of the pilar matrix. Based on a review of the clinical, microscopic, and investigational findings of the skin previously reported in association with her immunosuppressive drugs, we conclude that cyclosporine was the most likely causative agent. Moreover, hypertrichosis, dysmorphic facies, and tissue hyperplasia have all been observed in patients during cyclosporine administration.

POEMS syndrome is a rare condition with cutaneous manifestations commonly including angiomas, hypertrichosis, hyperpigmentation, and thickening of the skin. We describe a male patient with a 2-year history of cervical lymphadenopathy, erythematous thickening of the skin on the neck, and progressive walking difficulties. The patient had an occipital erythema with scarring alopecia and sparse follicular pustules at the edge of the lesion. Further investigation revealed symmetric polyneuropathy, hepatosplenomegaly, monoclonal gammopathy, subclinical thyreopathy, and an osteolytic bone lesion of the skull. Histologically, a plasmacytoma with lambda cell restriction was found. The overlying skin showed marked fibrosis, with loss of hair follicles, and a plasma cell infiltrate of polyclonal origin. The cervical lymph nodes showed histologic characteristics of multicentric Castleman's disease, and the skin of the neck showed thickening and vasoproliferation. There was no evidence of further plamacytomas. After excision of the plasmacytoma and postoperative irradiation, the symptoms gradually resolved within a few months. A cicatricial lesion remained on the occiput without further folliculitis or hair loss on the rest of the scalp. This case illustrates the reactive character of POEMS syndrome as a paraneoplastic syndrome in myeloma patients.

We describe a 46-year-old woman with multiple symmetrical papulocystic lesions on the face, neck, chest, back, and upper arms since childhood. Vermiculate atrophoderma, entropion, and progressive loss of eyelashes was also noted. Since the age of 30, 12 basal cell carcinomas have developed on the face. Histopathologic examination revealed multiple anastomosing nests and strands that arose from the lower part of a hair follicle in early lesions. In more advanced lesions, multiple keratinizing microcysts within a moderately sclerotic stroma were noted in the upper and mid dermis. In some biopsy specimens, focal areas showing sweat gland (ductal) and sebaceous differentiation were also observed. Basal cell carcinomas developed from the basaloid component of the hamartomatous proliferation.

Background: Pilomatricomas have a wide variety of clinical characteristics and are often misdiagnosed. This can result in extensive surgery for an essentially benign condition., Objective: The purpose of this study was to define the clinical and histologic spectrum of these tumors to aid diagnosis., Methods: Two hundred nine cases were analyzed retrospectively with regard to age at presentation, site, size, and physical appearance., Results: Pilomatricomas appear at any age, with peak presentation bimodally in the first and sixth decade. Their most common site is the head and neck. Presentation is of a hard nodule, either deeply subcutaneous and invisible or superficial with possible erosion through the skin surface. This may lead to a false diagnosis of malignancy or of an epidermoid cyst. An association with myotonic dystrophy has been confirmed, as is the rare occurrence of malignant transformation., Conclusion: Careful clinical examination and a high index of suspicion results in an accurate diagnosis, appropriate treatment, and the avoidance of unnecessarily extensive surgery.

Background: Extensive epidermal necrosis in newborn infants is an unusual event of heterogeneous cause., Objective: The objective of this article is to describe what seems to be a previously unrecognized lethal disease., Methods: The clinical and histopathologic features of three premature infants, two of them nonidentical twins, and the autopsy findings of one of them were analyzed., Results: Intrauterine lethal epidermal necrosis with hair follicle calcification, except for the face, hands, feet, elbows, and knees, was present in all three patients. Some histopathologic features were suggestive of epidermal apoptosis., Conclusion: We propose that the clinicopathologic alterations in our patients represent a new condition that may be caused by massive epidermal apoptosis.

Trichoepitheliomas (TEs) are benign follicular neoplasms that can be difficult to separate histologically from basal cell carcinomas (BCCs). It is important to make this distinction, because the treatments and prognoses differ for the two lesions. Previous reports have employed both histologic and immunohistochemical data in order to separate these two lesions. It is believed that transformation from a TE to a BCC is a rare event. We describe a case in which a single lesion with features of TE and BCC is present in a patient with multiple lesions of BCC.

Background: Tumor of the follicular infundibulum (TFI) is a rare benign adnexal tumor that has characteristic histopathologic features., Objective: Our purpose was to describe the clinical and pathologic features of 12 patients with TFI., Methods: Of 121,500 cutaneous biopsy specimens recorded between 1981 and 1993, all TFIs were identified and examined by conventional microscopy. The clinical and histologic findings were compared with those of previously published cases., Results: Of the 12 patients, seven had a solitary tumor, two had eruptive TFI involving the face, and three TFIs were incidentally discovered in association with nevus sebaceus or fibroma. TFI-like changes were also observed in the wall of a hybrid cyst. The most discriminating features of TFI were the horizontal platelike organization of the tumor and the dense elastic network beneath the tumor. Of the different forms of TFI, only eruptive tumors can be clinically identified because they are small hypopigmented macules., Conclusion: We classify TFIs as (1) solitary tumors, (2) eruptive tumors, (3) TFI associated with other lesions of Cowden's disease, (4) TFI associated with a single tumor such as nevus sebaceus, and (5) TFI-like epidermal changes.

Erythromelanosis follicularis faciei is an infrequently diagnosed disorder thought to be more common in men, with only seven reported cases in women. This condition consists of the clinical triad of well-demarcated erythema, hyperpigmentation, and follicular plugging on the face. We describe two additional female patients with this condition and present a review of the literature.

We describe a patient with multiple myeloma and cryoglobulinemia who had spicules with a horny appearance in the follicular openings of the face, particularly on the nose. Histopathologic study demonstrated that these spicules consisted of eosinophilic homogeneous deposits in the intercellular spaces between keratinocytes in the upper layers of the follicular infundibulum. Direct immunofluorescence, ultrastructural, and biochemical investigations revealed that these eosinophilic deposits were cryoprecipitates composed of IgG-kappa with electrophoretic characteristics identical to those of the paraprotein present in the serum of the patient. Hence we believe that these lesions are best referred to as pseudohyperkeratotic spicules of the nose, and that they are a characteristic cutaneous manifestation of patients with multiple myeloma and cryoglobulinemia.

Background: Bubble hair is an acquired hair shaft deformity characterized by bubble-like areas in the hair shaft seen with light microscopy and corresponding cavitary defects with scanning electron microscopy., Objective: Our purpose was to report the fourth case of bubble hair, to demonstrate a cause, and to determine whether the cavities contain gas or liquid., Methods: Light and scanning electron microscopy were performed. The patient's hair dryer was examined. We applied heat to normal hair of the patient and that of 16 human volunteers. Approximate temperatures for bubble formation were measured. The bubble contents were investigated by applying aqueous and nonaqueous liquids to affected hairs., Results: No person's hair failed to develop bubbles when subjected to sufficient heat. The cause of bubble hair in the patient was an overheating hair dryer. The cavitations contained a gas., Conclusion: Bubble hair is a reproducible hair shaft defect caused by heat. The use of overheating hair dryers, or any other hair care equipment that overheats, should be avoided.

Steatocystoma multiplex (SM) and eruptive vellus hair cysts (EVHC) share a clinical resemblance, but have distinctive histologic features. We describe a patient who had both SM and EVHC lesions and discuss the relationship between the two diseases. We believe that SM and EVHC are within the spectrum of the same disease process and could both be termed multiple pilosebaceous cysts.

Erythromelanosis follicularis faciei et colli is uncommon. Fewer than 20 cases have been reported. Except for one case in a woman and one case of unilateral distribution, all other reported cases have been bilateral in young male patients. We report the first case of unilateral distribution in a white girl.

The rational evaluation of hair disorders requires familiarity with follicular anatomy. Hair structure can be easily examined by studying clipped hair shafts, entire hairs gently pulled or forcibly plucked from the scalp, and scalp biopsies (sectioned vertically or transversely). Anatomic features will be different depending on whether a given hair is in the anagen, catagen, or telogen phase. Follicle size will also vary, from the minute vellus hair to the long, thick terminal hair. Each follicle can be divided into distinct regions--bulb, suprabulbar zone, isthmus, and infundibulum. Activity growing (anagen) hairs are characterized by a hair matrix surrounding a dermal papilla; inner and outer root sheaths are present and well developed. A catagen hair can be identified by its markedly thickened vitreous layer and fibrous root sheath, which surrounds an epithelial column; above this column, the presumptive club forms. A telogen hair is distinguished by its fully keratinized club, which is surrounded by an epithelial sac. Below this lies the secondary hair germ and condensed dermal papilla, waiting for the mysterious signal that initiates a new life cycle.

Trichothiodystrophy is a feature of several diseases that consist of characteristic hair shaft abnormalities and a wide spectrum of other developmental defects. Detection of sulfur-deficient hairs identifies this disorder and separates it from other similar ectodermal dysplasias with normal sulfur content. Detection of low sulfur hair syndrome is also important for genetic counseling, because the disease appears to be an autosomal recessive trait. We report a patient with chronic neutropenia, mild mental retardation, and low sulfur content in hair. Our case expands the spectrum of disorders associated with trichothiodystrophy.

We present the clinical and histologic features of the cutaneous lesions in a girl with cardio-facio-cutaneous syndrome. Marked tortuosity with hyperkeratosis of the sweat ducts and dystrophy of the hair shafts appear to be the cutaneous hallmarks of this syndrome.

Trichothiodystrophy appears to represent a central pathologic feature of a specific hair dysplasia associated with several disorders in organs derived from ectoderm and neuroectoderm. The key finding is brittle hair with low sulfur content, but alternating dark and light bands under polarizing microscopy, trichoschisis, and absent or defective cuticle are additional important clues for the diagnosis of trichothiodystrophy. Our review of the literature revealed extensive associated findings in trichothiodystrophy. Classification of patients with trichothiodystrophy and other dysplasias is difficult because diminution of sulfur-rich protein in hair is not a sufficient marker to allow precise differentiation, although several similar ectodermal dysplasias can be excluded by demonstration of abnormal sulfur content in hair of patients with trichothiodystrophy. Patients with trichothiodystrophy should have a thorough evaluation for other associated manifestations, including investigation of photosensitivity and DNA repair defects. Detection of low-sulfur brittle hair syndrome is also important for genetic counseling because the disease appears to be inherited in an autosomal recessive pattern.